1. Field of the Invention
The present invention relates to a differential apparatus which is provided on a motor vehicle.
2. Related Art
Patent Document 1 discloses a differential apparatus in which a case is formed of a one-piece member. In the differential apparatus of Patent Document 1, a working tool is inserted into the case from an opening therein so as to machine an interior of the case to produce a spherical inner space defined by a spherical inner surface. A pinion gear and a pair of side gears are inserted into the spherical inner space, and back sides of these gears are supported on the spherical inner surface. Spherical washers are interposed between the back sides of the gears and the spherical inner surface.
In this differential apparatus, external and internal shapes of the case can be simplified, and the machining is facilitated. In addition, the pinion gear and the pair of side gears are assembled together in a compact fashion for disposition in the interior of the case.
In addition, meshing reaction forces of the pinion gear and the pair of side gears are slidingly supported on the spherical back sides of the gears. Therefore, the sliding frictional properties of the gears are stable, and the durability of the gears is high.
However, when this differential apparatus is mounted on a vehicle, in the event that frictional resistances of a left wheel and a right wheel with a road surface come to differ, due to the characteristics of this differential apparatus, it becomes difficult to transmit a driving force which is equal to or greater than the driving force of the wheel with a lower frictional resistance.
This problem has conventionally been understood as a technical problem which is inherent in a differential apparatus having no differential action limiting function (referred to as a so-called “conventional-differential”) due to the configuration and function thereof.
In contrast with this conventional-differential, various types of differential apparatuses with a differential action limiting function (referred to as a so-called limited slip differential (LSD)) are used on sport-type and 4WD vehicles.
Even in a general vehicle with a conventional-differential, such a differential action limiting function would be effective when attempting to increase the starting and hill-climbing properties thereof.
Patent Document 2 discloses a differential apparatus in which a case is formed of a one-piece member, and a pinion gear and a pair of side gears are inserted from an opening in the case. In the differential apparatus of Patent Document 2, a differential action limiting function is provided by tapered surfaces formed on the pair of side gears and the case.
However, according to the differential apparatus of Patent Document 2, in order to provide the differential action limiting function, it is required to form the tapered surfaces on the case and the pair of side gears, which causes the following problems.
First, a severe machining accuracy relating to a tapering angle is required to the tapered surfaces, which increases mashing manhours.
Second, the tapered surface is provided on an external side of the side gear, and therefore, the differential apparatus is enlarged in both radial and axial directions.
Third, although Patent Document 2 also discloses a differential mechanism as another embodiment which uses a multi-plate clutch as a differential action limiting function device, it is obvious that the number of parts involved is increased, and the differential apparatus is enlarged.    [Patent Document 1] JP-A-2009-250320    [Patent Document 2] JP-A-2003-294109